The invention relates to an arrangement of a rear-axle module on a vehicle body for a two-axle, two-track vehicle which is at least partially electrically driveable by an electric motor, wherein the rear-axle module has a rear-axle member designed for the fastening of wheel-controlling links of a rear axle, and has a housing for receiving components for providing electrical energy, wherein, in a state in which it has been arranged on the vehicle body, the housing is arranged in a front region of the rear-axle module and is fastened to the rear-axle member or forms a constituent part of the rear-axle member, and wherein the rear-axle module is attached to the vehicle body from below by way of two rear-axle member bearings, which are situated to the rear in the direction of travel and which are arranged in a rear end region of the rear-axle module, and by way of two middle rear-axle member bearings, which are arranged in a middle region of the rear-axle module.
The invention also relates to a rear-axle module for an arrangement of said type, and to a two-axle, two-track vehicle which is at least partially driveable by an electric motor and which has an arrangement of said type.
The provision of an adequate amount of electrical energy for a two-axle, two-track vehicle which is at least partially driveable by an electric motor constitutes a major challenge firstly with regard to the required structural space and secondly owing to the high additional weight of the components required for generating the electrical energy. In particular, there is a conflict of aims with regard to comfort, acoustics and driving dynamics. In order to implement an electric drive in abovementioned vehicles in a manner which satisfies requirements, that is to say in hybrid vehicles (driveable partially by an electric motor) or in purely electric vehicles (driveable only by an electric motor), it is necessary for the electrical components required for this purpose, that is to say the batteries for generating the electrical energy and the associated power electronics, to be accommodated in the vehicle, or arranged on the vehicle body, in the most weight-saving or weight-optimized and structural space-saving or structural space-optimized manner possible.
From the prior art, for example from German patent publication no. DE 10 2011 081 836 A1 or International patent publication no. WO 2012/065787 A1, it is known for the components for generating electrical energy to be arranged in a housing which is arranged on the rear-axle member or in a housing which forms the rear-axle member, wherein normally, the rear-axle member and the housing are preassembled together with other components, such as for example the rear-axle differential or the wheel-controlling links of the rear axle, to form a so-called rear-axle module, and are subsequently fastened as a unit to the vehicle body or to a vehicle bodyshell. Here, for reasons relating to acoustics and comfort, the rear-axle module is preferably fastened to the vehicle body by way of four rear-axle member bearings which are received in the rear-axle member and which are in the form of rubber bearings or hydraulically damped bearings.
It is thus an object of the present invention to provide an improved arrangement of a rear-axle module on a vehicle body for a two-axle, two-track vehicle which is at least partially electrically driveable by an electric motor, by means of which arrangement the abovementioned conflict of aims can be better resolved.
Accordingly, a rear-axle module according to the invention is characterized in that it is additionally attachable or connectable to the vehicle body by way of two front bearings which are arranged on the housing in the front region of the rear-axle module, and a two-axle, two-track vehicle according to the invention which is at least partially electrically driveable by an electric motor, and which has a rear-axle module, is characterized in that it has a rear-axle module according to the invention, which is arranged on the vehicle in accordance with the invention.
Here, in the following text, a rear-axle module is to be understood to mean a preassembled unit of parts and/or components, which preassembled unit is, during the assembly process, connected as a unit to the vehicle body or to a vehicle bodyshell.
Here, the rear-axle member is preferably a subframe or of frame-like form and, in a state in which it has been arranged on the vehicle body or vehicle bodyshell, said rear-axle member is arranged in a rear region of the rear-axle module, that is to say, during forward travel of the vehicle, the rear-axle member is arranged toward the vehicle rear end in the vehicle longitudinal direction, wherein the rear-axle member preferably forms the rear region of the rear-axle module. The rear-axle member preferably has two crossmembers, one front and one rear, which extend substantially perpendicular to the vehicle longitudinal direction and which are furthermore preferably connected to one another by way of two longitudinal members which extend substantially in the vehicle longitudinal direction. On the crossmembers themselves, there are preferably provided bearing receptacles for a rear-axle differential, wherein preferably, a 3-point bearing arrangement is provided, with two bearing receptacles in the front crossmember of the rear-axle member and one bearing receptacle in the rear crossmember, wherein, for reasons relating to acoustics and comfort, the rear-axle differential is preferably attachable to the rear-axle member by way of elastic rubber bearings. It is however also possible for an electric motor to be fastened to the rear-axle member. For the fastening of wheel-controlling links, bearing lugs or the like are preferably provided on the rear-axle member.
The housing for receiving components for the provision of electrical energy is in this case arranged, in a state in which it is arranged on the vehicle body or on the vehicle bodyshell, in a front region of the rear-axle module as viewed in the vehicle longitudinal direction during forward travel of the vehicle, that is to say in the direction of the front of the vehicle, and said housing preferably forms, by way of a front part, the front region of the rear-axle module. The rear part of the housing is preferably connected to the rear-axle member. The rear housing part may however also form a part of the rear-axle member, for example the front crossmember, whereby particularly advantageous utilization of the available structural space is made possible.
The housing is preferably at least partially a cast housing, and is in particular designed such that components received therein can be protected against environmental influences, in particular against moisture. Here, the housing may also comprise multiple individual housings and/or be assembled from multiple parts. It is furthermore preferable for the housing to likewise be designed for the connection of wheel-controlling links.
Components for storing electrical energy which can be received in the housing are for example high-voltage storage cells or high-voltage storage cells combined in each case to form high-voltage storage modules, that is to say components which provide a voltage from 200 V to 400 V. It is however also possible for fuel cells with associated accumulators to be received therein, or conventional accumulators, for example one or more conventional 12 V vehicle batteries. In this case, it is advantageous for the associated power electronics to likewise be received in the housing.
For the attachment of the rear-axle module to the vehicle body, two rear-axle member bearings are provided inter alia in the rear end region of the rear-axle module. Said rear-axle member bearings are preferably arranged in the rear corner regions of the rear-axle member, for example in the end regions, in particular at the ends, of the crossmembers or of the longitudinal members of the rear-axle member. The rear-axle member may however also have supporting arms which project obliquely rearward and outward, with the rear-axle member bearings then being arranged at the outer ends of said supporting arms.
Furthermore, in the middle region of the rear-axle module, there are provided two rear-axle member bearings for the connection of the rear-axle module to the vehicle body. In this case, the middle region is not imperatively a region arranged around the geometrical middle which lies in the vehicle longitudinal direction, but is a region which lies between the front region and the rear region as viewed in the vehicle longitudinal direction. In particular, the middle region is a connecting region in which the housing, which is arranged in the front region or which forms the front region, is connected to the rear-axle member, which is arranged in the rear region or which forms the rear region.
What has proven to be particularly advantageous is the use of hydraulically damped rear and middle rear-axle member bearings, in particular rear and middle rear-axle member bearings which are hydraulically damped in the vehicle longitudinal direction.
According to the invention, it is furthermore the case that two front bearings are provided which are arranged on the housing in the front region of the rear-axle module, by which bearings the rear-axle module is attached to the vehicle body. In this way, the oscillatory characteristics of the rear-axle module or of the vehicle, in particular with regard to pitching oscillations, that is to say with regard to oscillations about a vehicle transverse axis (Y axis), can be positively influenced, such that acoustics and in particular comfort can be improved. The additional support of the rear-axle module in its front region furthermore has the effect that the middle rear-axle member bearing is relieved of load, such that the latter can be designed to be of smaller dimensions in relation to the attachment of the rear-axle module only by way of a total of four bearings, as is known from the prior art.
It is preferably the case that the middle rear-axle member bearings, in particular the middle and rear rear-axle member bearings, from a conventional vehicle, that is to say from a vehicle driven only by an internal combustion engine, are carried over for the hybrid variant. This means that, despite the high additional weight arising from the components for storing electrical energy, the rear-axle member bearings do not have to be designed to be of larger dimensions. As a result, further components for the attachment to the vehicle body, such as for example the bearing receptacles on the vehicle body or on the rear axle member, can likewise be carried over. Furthermore, for a hybrid vehicle, no additional structural space is required for the rear-axle member bearing in relation to a conventional vehicle.
By the housing which is integrated in the rear-axle module, it is possible for components received therein to be quickly and easily integrated into the vehicle or arranged on the vehicle body. Furthermore, the available structural space is optimally utilized. Through the possibility of designing the housing to also receive wheel-controlling links or other corresponding parts, it is possible for the attachment points in the case of the hybrid variant to be arranged geometrically identically to those in the conventional vehicle, which allows multiple parts to be carried over, and thus increases the economic viability of the hybrid variant.
Here, it is preferably the case that the two additional front bearings are arranged in the region of a front edge or directly at the front edge of the housing or of the rear-axle module. Here, said bearings are preferably designed and arranged on the housing such that they can be attached to the vehicle body, in particular to the vehicle bodyshell, from below, that is to say they can be supported on the vehicle body from below.
In a particularly preferred refinement of the invention, the rear-axle module is, by way of the two additional front bearings, attached to the vehicle body in the region of a footwell, in particular of a rear footwell, that is to say in particular in the region of the footwell in the rear-seat compartment, in particular in a heel region of the rear footwell. Here, the heel region refers to that region of the rear footwell on the vehicle body or on the vehicle bodyshell which surrounds the heels or the feet of a rear-seat passenger in a normal seating position, that is to say refers to the corresponding part of the floor of the rear footwell and to the rear wall of the footwell below the seat bench, in which a rear-seat passenger places his or her feet. In the case of a vehicle without a rear-seat compartment, for example in the case of a two-seat vehicle, the attachment of the rear-axle module to the vehicle body or to the vehicle bodyshell is preferably correspondingly realized in a rear region of a front footwell, that is to say correspondingly in the rear region of a driver or front passenger footwell, behind the seats.
In a refinement of the invention, the two additional, front bearings arranged on the housing, by means of which bearings the rear-axle module is additionally attached in the front region to the vehicle body, are elastomer bearings. Here, the elastomer bearings are preferably designed to be at least three times as stiff in a z direction, that is to say along the vehicle vertical axis, as in an x direction, that is to say in the vehicle longitudinal direction. In particular, the two front additional bearings have stiffnesses in x, y and z directions which are in a ratio x:y:z of 2:5:7. Said ratio has proven to be particularly advantageous with regard to the conflict of aims in terms of acoustics, comfort and driving dynamics.
In one refinement of the invention, the housing has an upper shell and a lower shell, wherein, when the housing is in an assembled state and the rear-axle module is in a state in which it has been arranged on the vehicle body, a parting joint between the housing upper shell and the housing lower shell preferably runs obliquely downward through the housing from top front to bottom rear as viewed counter to a vehicle longitudinal direction.
In this way, in the case of a housing formed by casting, that is to say in the case of a housing upper shell formed by casting and a housing lower shell formed by casting, the necessary draft angles required for demolding purposes after the casting process are distributed approximately uniformly between the two housing shells, whereby the internal volume of the housing can be enlarged, such that more structural space is available for the components that are to be arranged in the housing.
In a preferred refinement, the middle rear-axle member bearings are integrated into the housing, preferably in the middle region of the rear-axle module, in particular in the connecting region or in a region directly adjacent thereto. Here, in the case of a housing with housing upper shell and housing lower shell, the middle rear-axle member bearings are preferably integrated into the housing upper shell. In this case, the above-described profile of the parting joint has the further advantage that the parting joint runs not through but past the bearing receptacles of the middle rear-axle member bearings.
In a preferred refinement of the invention, the housing is of catamaran-like form and has two housing hulls which are arranged substantially parallel to the vehicle longitudinal direction, wherein one of the two front additional bearings is arranged in each case in the front region of a housing hull.
Here, the housing hulls are preferably connected to one another in the front region and/or in the middle region of the rear-axle module. For the connection of the housing hulls in the front region, provision is preferably made of one or more substantially vertically arranged plates which extend transversely with respect to the vehicle longitudinal direction, whereas a front crossmember of the rear-axle member is preferably provided for the connection of the housing hulls in the middle region and/or at the rear ends thereof.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.